Method of pre-heating a refractory lined vessel



R. E. LYMAN A ril 15, 1969 Sheet Filed May 23, 1967 2 INVENTOR R/CHARO5.1mm By M M Attorney 5.5m .SSE k Wm Vb April 15, 1969 R. E. LYMAN3,439,072

METHOD OF FEE-HEATING A REFRACTORY LINED VESSEL Filed May 23, 1967 Sheet2 of 2 m VE/VTOR RICHARD E. LYMA/V A/larney United States Patent3,439,072 METHOD OF PRE-HEATING A REFRACTORY LINED VESSEL Richard E.Lyman, Homewood, Ill., assignor to United States Steel Corporation, acorporation of Delaware Filed May 23, 1967, Ser. No. 640,749 Int. Cl.F27d N16 US. Cl. 26352 9 Claims ABSTRACT OF THE DISCLOSURE A method ofpreheating a refractory lined vessel prior to receiving molten steel inwhich a mixture of fluid hydrocarbon fuel and oxygen is burned withinthe vessel with the oxygen-to-fuel ratio being maintained sufli-cient-1y low to produce combustion products which will be reducing to ironoxides at the temperature within the vessel. Thus, there will be nomolten iron oxide to dissolve the refractory lining.

This invention relates to a method of preheating a refractory linedvessel and more particularly to preheating the vessel prior to fill-ingit with molten steel or other ferrous metal. The method is particularlyapplicable for use with continuous inline liquid steel degassingapparatus which is preferably preheated to a temperature between 2700and 3000 F. These temperatures eliminate the need for extra super heatin the steel, prevent freezing during degassing, and eliminate the needfor skulling and chipping of the lining of the degassing apparatus. Suchpreheating is also advantageous and sometimes essential in the handlingof steel in other operations such as continuous casting. Prior to myinvention the preheating was done by conventional forced air combustion.The products of this combustion are highly oxidizing at hightemperatures to steel remaining in the vessel as the result of splatter,skulling or incomplete draining. Thus, such preheating resulted in theformation of viscous slags containing higher oxides of iron andiron-oxide refractory solutions. At these high temperatures therefractories of the lining are soluble in molten iron oxide. In additionto plugging restricted openings within the preheated vessel these ironoxide slags contain substantial quantities of oxygen which maycontaminate and alter the chemical composition of the steel beingprocessed.

It is therefore an object of my invention to provide a method ofpreheating refractory lined vessels which are free of the disadvantagesof conventional forced air combustion.

This and other objects will be more apparent after referring to thefollowing specification and attached drawings, in which:

FIGURE 1 is a schematic view of apparatus used in degassing moltensteel;

FIGURE 2 is an enlarged view of the burner used in my invention; and

FIGURE 3 is a view taken on the line III-III of FIGURE 2.

Referring more particularly to FIGURE 1 of the draw ings, referencenumeral 2 indicates a degassing chamber having a refractory lining 4 andan inlet 6 for receiving molten steel. An outlet 8 is connected to avacuum pump not shown. The degassing chamber 2 is connected by means ofa vertical duct 10 and a horizontal duct 12 to a pouring box or tundish14. The ducts 10 and 12 and tundish 14 are lined with refractory 16. Anopening 18 in the bottom of the tundish 14 is located above a runner 20.An overflow opening 22 is provided in the tundish 14. No novelty isclaimed for this apparatus which may be considered conventional insofaras the present invention is concerned. Apparatus such as shown in mycopending application Ser. No. 511,513 filed Dec. 3, 1965, isillustrative of vessels which may be preheated according to the presentinvention.

According to my invention I provide a burner or gas injector 24 fordelivering fuel and oxygen through a port 26 into the degassing chamber2 and a similar burner 28 for introducing fuel and oxygen into thetundish 14. Since the burners 24 and 28 are essentially duplicates, onlyburner 24 will be described in detail. As shown in FIGURES 2 and 3,burner 24 includes two concentric tubes 30 and 32 with a partition 34extending between the inner wall of tube 30 and the outer wall of tube32 intermediate their ends. A collar 36 is attached to the forward endof tubes 30 and 32 and bears against a water cooled collar 38 at theentry end of port 26. Collar 36 is provided with a cooling water chamber40 having diametrically aligned partitions 42 therein with openings 44ther'ethrough. Tubes 46 extend through partition 34 and collar 36 to thedischarge end of the burner. Shorter tubes 48 extend through "and aresupported by the walls of collar 36. Cooling water enters chamber 40through inlet 50 and passes between and around tubes 46 and 48 andthrough openings 44 to outlet 52. A sight opening 54 in line with tube32 is covered with a sight glass 56.

Fuel is introduced through conduit 58 into tube 30 and passes throughtubes 46 into the chamber 2. Oxygen is introduced through conduit 60into tube 30 around tubes 46 and passes through tubes 48 into thechamber 2. Valves 62 and 64 are provided for controlling flow of fueland oxygen to the burner. The fuel used is preferably natural gas whichis substantially all methane, but may also be any suitable fluidhydrocarbon fuel such as atomized fuel oil or fluidized powdered coal.The oxygen need not be pure oxygen, but must be a gas containing atleast 50% oxygen. It is preferred that commercially pure oxygen be used.The oxygen-to-fuel ratio is adjusted to a value that will result in acombustion product composition that is reducing to iron oxides at hightemperatures and yet sufficient to provide the necessary heat ofcombustion. With any fluid hydrocarbon fuel the CO to CO ratio ismaintained between 0.06 and 0.22. When natural gas is the fuel, thevolumetric oxygen-to-fuel ratio is between 0.8 and 1.1. With this ratiobeing maintained the gas firing rate is set at a value that will providethe desired preheating temperature. The injection velocities of the fueland oxygen are maintained above the rate of flame propagation and shouldbe maintained well below sonic velocities. It is preferred to have thevelocities between 50 and 600 ft. per second. Burning of the fuel andoxygen is continued until the refractory lining has been heated to thedesired temperature which is generally between 2700 and 3000 F. Theproducts of combustion pass out through opening 6. The firing is thendiscontinued and a ladle L filled with molten steel is then positionedover opening 6 and the chamber 2 and tundish 14 evacuated in the usualmanner.

While one embodiment of my invention has been shown and described, itwill be apparent that other adaptations and modifications may be made.

I claim:

1. A method of preparing, for receiving molten ferrous metal, arefractory lined vessel having ferrous metal on the inner surface of therefractory, said refractory being soluble in molten iron oxides atelevated temperatures, which method comprises injecting fluidhydrocarbon fuel and oxygen into the vessel, burning said fuel andoxygen, maintaining the oXygen-to-fuel ratio sufliciently low so thatthe combustion products resulting from their burning will be reducing toiron oxides at the temperature within the vessel, and maintaininginjection velocities of the fuel and oxygen above the rate of flamepropagation.

2. The method of claim 1 in which the CO to CO ratio in the combustionproducts is between 0.06 and 0.22.

3. The method of claim 2 in which the injection velocity of the fuel andoxygen is between 50 and 600 ft. per second.

4. The method of claim 1 in which the surface of the refractory liningis heated to a temperature at which the iron oxide becomes molten.

5. The method of claim 4 in which the CO to CO ratio in the combustionproducts is between 0.06 to 0.22.

6. The method of claim 5 in which the injection velocity of the fuel andoxygen is between 50 and 600 ft. per second.

7. The method of claim 1 in which the fuel is natural gas and thevolumetric oxygen-tofuel ratio is between 0.8 and 1.1.

8. The method of claim 7 in which the surface of the refractory liningis heated to a temperature at which the iron oxide becomes molten.

9. The method of claim 8 in which the injection velocity of the fuel andoxygen is between 50 and 600 ft. per second.

References Cited UNITED STATES PATENTS 1,675,735 7/1928 Stohr 264-301,900,223 3/1933 Burke 263-52 3,148,272 9/1964 Aitken et a1. 26430 JOHNJ. CAMBY, Primary Examiner.

U.S. C1. X.R. 26430

